Tiny Core Plus works well the Raspberry Pi and it connects to wifi.Mine is set up with openbox and xfe.

Citer

CorePlus is an installation image and not the distribution. It is recommended for new users who only have access to a wireless network or who use a non-US keyboard layout. It includes the base Core System and installation tools to provide for the setup with the following options: Choice of 7 Window Managers, Wireless support via many firmware files and ndiswrapper, non-US keyboard support, and a remastering tool.